Two aluminum alloy plates each 10 mm thick and 1 m long are welded without crowning by multi-pass tungsten inert gas butt welding. The joint configuration is V-type with 60∘ angle and root gap is maintained at 5 mm. If electrode of 5 mm diameter with 500 mm length is used for welding, then the number of electrodes required is(A) 7 (B) 9 (C) 11 (D) 13